Conical antennas, which include a single inverted cone over a ground plane, and biconical antennas, which include a pair of cones oriented with their apexes pointing toward each other, are used as broadband antennas for various applications.
Excitation of biconical dipoles is accomplished by imparting an electrical potential across the apex of the two opposing cones, causing a TEM mode. This mode is analogous to the TE01 mode of sectoral horns, but as the biconical dipole is a complete figure of revolution, symmetric about the cone axis, the TEM mode results. In a biconical dipole, excitation is by the dipole moment formed across the horn walls (opposing cones), so the structure is self exciting. A biconical dipole antenna is an example of an omni-directional vertically polarized antenna of relatively great bandwidth.
TE10 modeling of conventional biconical dipole structures has been proposed for the purpose of horizontal polarization and omni-directional radiation. In one instance, a circle of wire operates as a loop antenna and an excitation probe, and is placed normal to the bicone axis. For example, U.S. Pat. No. 7,453,414 discloses a biconical loop antenna that is the dual to the biconical dipole antenna, and has broadband omni-directional horizontally polarized radiation. This patent is assigned to the current assignee of the present invention, and is incorporated herein by reference in its entirety.
The cone is an example of an Euclidian geometry. Euclidian geometries often provide excellent antenna shapes. In terms of geometry, a cone is a solid figure bounded by a plane base and a surface called the lateral surface formed by the locus of all straight line segments joining the apex to the perimeter of the base. The first instance of a cone as an antenna may be unknown, but the textbook “Antennas”, 2nd edition, by John Kraus, W8JK, states that Sir Oliver Lodge constructed a biconical dipole antenna by 1897.
Even in view of the advances made in biconical antennas, there is still a need for such an antenna that supports both vertical polarization and horizontal polarization.